Airflow conduits within motor vehicles may be used to circulate air as part of the heating, ventilation and air-conditioning (HVAC) system. The airflow conduits may be used to circulate heated or cooled air to various locations within the motor vehicle. For example, exemplary airflow conduits may be arranged beneath the instrument panel, center console, the floor carpet or the roof headliner. Such airflow conduits may direct airflow towards the windshield, footwells, seats and otherwise throughout the passenger compartment. The air may be fresh (ambient) air from outside of the vehicle, recirculated air from within the vehicle or a combination thereof.
Airflow conduits may be blow molded from a thermoplastic composition. While blow molded airflow conduits are relatively inexpensive to produce, the blow molded airflow conduits may exhibit certain drawbacks.
The blow molded airflow conduits may suffer from relatively low thermal efficiency, such that the heated or cooled air being transmitted therein may substantially decrease or increase in temperature, respectively, before the air reaches the passenger compartment. The blow molded airflow conduit may also vibrate and/or contact against other motor vehicle components during operation of the vehicle, which may result in squeaking, rattling or other unwanted noise.
In order to reduce unwanted noise with adjacent components, a localized foam element may be glued onto the blow molded airflow conduit at a location indicative of the source of unwanted noise, such as at a location where the blow molded airflow conduit may make contact with another component (e.g. rub against) when the vehicle is being operated.
In order to increase thermal efficiency, particularly at the inlet and/or outlet to the blow molded airflow conduit where the conduit may mate with another component, the mating edge of the blow molded airflow conduit may include a localized foam seal intended to seal the connection formed between the mating components to inhibit airflow losses. Similar to the foam element used for noise attenuation, the foam seal may be glued to the blow molded thermoplastic airflow conduit with a separate adhesive. In both instances, the adhesive may be a hot-melt adhesive or a pressure sensitive adhesive.
Unfortunately, while the use of a foam seal particularly only at locations where the blow molded airflow conduit mates with other components may reduce airflow losses, such does not address the thermal losses encountered by air as it flows along the length of the blow molded airflow conduit.
Furthermore, the use of an adhesive to glue the foam seal or other foam element to the blow molded airflow conduit is problematic, in that the bond may degrade over time and ultimately fail.